It is, however, known from GB 2027581 to mould the interior sole integrally with the outsole.
It is also known to use a method of the above type for moulding an outsole integrally with an interior sole on an upper to obtain a shoe with a low sole. At the known method a last is used having a very thin rib defining the wedge-shaped recess forming the interior sole so as to allow the interior sole to abut the inner face of the upper as closely as possible. However, the use of the very thin, projecting rib entails that the last has to be made of a hard metal, such as steel or hard aluminium, to prevent deformation of the rib when it is subjected to the closing pressure of the sole mould. The manufacture of shoe lasts in a hard metal is, however, considerably more expensive than the manufacture of shoe lasts in a plastic material, for which reason the use of metal lasts increases the shoe production costs significantly. Furthermore, in practice it has proved difficult to completely avoid deformation of the thin projecting rib on the last.